Well, that 2GB stick didn't work with either of the others, nor by itself, so I'm declaring it dead and will be in touch with Crucial for a replacement, which I'll then keep as a spare. The only thing I didn't think of checking was to put either of the working ones in by itself, just to check the machine would run with only 2GB (nothing in the mboard manual to say it wouldn't, just that the manufacturer supplies them with 3GB minimum).1024MAK wrote: If your machine supports a single card of RAM, check it will work with just one of each to see if you have a non-functional RAM card. It may also be worthwhile carefully cleaning the RAM card connector if it has accidentally been touched or has become dirty..
Then, as you have done, try combinations. In theory you want two of exactly the same. But some systems are happy with different RAM cards.
Generally, if it works for three hours, the system will be reliable. You may also want to download and use a RAM tester. I have used an older version of this Memtest86 http://www.memtest86.com/ but have not used the newer version on the web site. I burnt a copy to a bootable CD. I then let it run for three to four hours.
Good luck
Mark
The PC has now run for 24 hours OK with one old and one new 2GB cards, reporting 4GB in total and seems to be performing well without the usual non-stop hard disk activity (probably indicating the swap file use is down thanks to extra RAM).
Thanks to everyone, as usual got a lot more useful advice here than I would have done on many a PC forum.